Two words:
Protein Spill.
:drevil:
But really, for most people it isn't bad. Every so often, you'll get someone who gets sick, but they mostly don't, uh, release anything until they reach a bathroom. Only in rare cases does it actually spill in the ride, and then they need to shut down one of the four simulator rooms for cleanup. But a word of warning.... If you've never been on Mission: SPACE, you really might not know for sure what the effects on YOU will be like. I just said that very few people get sick, but you really never know. My mom went on it once, spent the ride screaming her lungs out, the next half hour in the bathroom, the next two weeks making sure she only faced forward in the buses, and the next month trying not to look at the sky. And she still feels queasy in the France show, during the part where the camera looks up at the Eiffel Tower (it reminds her too much of the launch tower). Just a warning.